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Java Basics. - Prashant Nagaraddi. Features of Java. Java syntax is similar to C/C++ but there are many differences too Java is strongly typed like C++ Type inconsistencies are detected at compile time Java is an Object-Oriented Language
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Java Basics - Prashant Nagaraddi
Features of Java • Java syntax is similar to C/C++ but there are many differences too • Java is strongly typed like C++ • Type inconsistencies are detected at compile time • Java is an Object-Oriented Language • Computation is achieved via interacting objects (more on this later)
Features of Java • Java is an interpreted language • Java source code is translated into Java bytecodes by Java compiler • These form the instructions to a Java Virtual Machine (Java VM) • The Java VM interprets the bytecodes and as a result, executes real machine instructions Source Code bytecode compiler bytecode file Interpreter (VM) Hello.java javac Hello.class java
Features of Java • Java bytecodes are machine independent • This means that you can • compile Java source code on one platform • transfer the bytecodes to another platform and • execute them using a Java VM that has been ported for that platform • You can also send Java bytecodes around the Internet as data. Sending code around in this manner is called providing executable content
Running the Java Compiler (javac) and Interpreter (java) • On the CS dept. Solaris systems • the latest compiler, interpreter and class sources (J2SE) are in the directory /usr/j2se • the compiler and interpreter are in the /usr/j2se/bin directory. This should be included in your PATH • to run the compiler, just give the name of a .java file • % javac Hello.java • to run the interpreter, give the name of the bytecode file without the .class extension • % java Hello • Hello, World
Running the Java Compiler (javac) and Interpreter (java) • On Windows 9x/2000/NT • you can compile and run your programs using • the Java 2 Standard Development Kit (SDK) for Windows • Latest I’ve tried is J2SEv1.3 available from http://java.sun.com • Add the “bin” directory in your java directory to your DOS PATH • Compile and run just like in Solaris • a commercial Java Interactive Development Environment (IDE) such • Visual J++ (http://msdn.microsoft.com/visualj/) • CodeWarrior (http://www.metroworks.com) • VisualCafe (http://www.visualcafe.com)